New approach to precisely measure gamma-ray intensities for long-lived fission products*

The distribution of fragment masses following fission, called fission yields, is one of the most basic quantities of nuclear fission. These fission yields play an important role in many applications such as estimation of decay heat and delayed neutron emission in nuclear reactors, the reactor neutrino study, the radio-isotope production for medical applications, stockpile stewardship, and national security. One of the most straightforward and reliable ways to determine the number of fissions that occurred in a chain reaction is done via detection of the characteristic γ-rays emitted during the β decay of the long-lived fission products. A lot of nuclear data suffer from high uncertainties, which contribute to the uncertainties in the determined fission yields. We developed a new experimental method [1] that takes advantage of radioactive ions beam at CARIBU, and very well characterized detection system [2], to performed precision. We will present results for ¹⁴⁴Ce and ¹⁴⁷Nd decay properties determined to fractional precisions of ~1%, and discuss plans for future measurements.

[1] K. Kolos, et. al., "New approach to precisely measure gamma-ray intensities for long-lived fission products, with results for the decay of ⁹⁵Zr" Nucl. Instrum. Methods A 1000 165240 (2021)

[2] R. G. Helmer, et. al., Nucl. Instrum. Methods A 511 360 (2003)